An effective dispersive liquid-liquid microextraction method for pharmaceutical extraction: Optimization via central composite design

23 In this study, a simple and efficient dispersive liquid-liquid microextraction procedure (DLLME) 24 was developed to remove diclofenac sodium (DF) from water samples. Various parameters such 25 as diclofenac concentration in aqueous phase (10-50 mg/L), process time (2-10 min), extraction 26 solvent concentration (0.005-0.025 M), and centrifuge speed (1000-5000 rpm) were investigated. 27 The experimental design was performed by the Response Surface Methodology (RSM) 28 according to the central composite design to reduce the number of experiments and determine the 29 optimal extraction conditions. The effect of the single and simultaneous operational parameters 30 was evaluated. In this regard, the extraction concentration of 0.01 M, the initial diclofenac 31 concentration in aqueous phase 20 mg/L, the rotation speed of the centrifuge 4000 rpm, and the 32 residence time of 8 min were obtained as the optimum operating conditions. According to the 33 other studies and available findings, the ratio of two-phase organic and aqueous discharges 34 (Q org ⁄Q aq ) was set to 1:9. The diclofenac extraction from the aqueous phase was 77.91% in 35 optimum operating conditions. 36